Recently, a study or technology development for improving transmission speed in a mobile communication scheme is in an active progress. For example, a method for using a wideband signal in order to improve a transmission speed in a mobile communication scheme exists. Here, to transmit a wideband signal faster, a submillimeter wave of a frequency higher than a microwave that is being used up to now needs to be used. However, in case of using a signal of a high carrier frequency, an electric energy loss increases. Therefore, in case of using a signal of a high carrier frequency, a service area that may provide a mobile communication service reduces or an electric energy loss increases remarkably.
Accordingly, as a compensation technology for compensating for an electric energy loss, an antenna array technology that secures circuit quality by means of an array gain draws an attention. As an antenna array technology, a technology disclosed in Japanese Patent Publication No. 2008-205645 exists.
To obtain a larger array gain, a large number of antenna elements (referred to as an ‘array device’ hereinafter) compared to the conventional phased array antenna for reception of a microwave is required. However, in case of having a frequency converter and an Analog-to-Digital Converter (ADC) in each array device and performing a signal reproduction process or an orientation (phase) control process based on a reception signal received by each array device, a circuit scale or a device scale regarding signal processing of a received signal increases.
In this case, it may be possible to reduce a circuit scale or a device scale by performing synthesis of a received signal received by each array device using an analog circuit that processes an intermediate frequency signal. However, in case of performing synthesis of a received signal received by each array device using an analog circuit that processes an intermediate frequency signal, a method of a higher function (for example, a method of a higher accuracy) cannot be used in a process regarding signal detection or an orientation control process, etc. Therefore, in case of performing synthesis of a received signal received by each array device using an analog circuit that processes an intermediate frequency signal, it is difficult to optimally adjust a direction in which a transmitter that transmits an orientation signal is positioned, or achieve a high signal detection characteristic when a direction in which the transmitter is positioned and a beam direction are dislocated.
As a method for solving this problem, like a technology described in Japanese Patent Publication No. 2008-205645, a method for grouping a plurality of array devices forming a phased array antenna, performing synthesis of a received signal received by each array device in each sub array where array devices have been grouped to carry out a signal reproduction process or an orientation control process. In case of performing synthesis of a received signal received by each array device in each sub array to carry out a signal reproduction process or an orientation control process, a circuit scale or a device scale may be made smaller than a case of preparing a frequency converter or an A/D converter in each array device, and a method of a higher function may be used.
For example, in the technology described in Japanese Patent Publication No. 2008-205645, a communication unit performing an orientation control process corrects an amplitude or a phase based on an already known reference transmission signal (for example, a signal corresponding to a trading signal) transmitted from a transmitter. However, since the technology described in Japanese Patent Publication No. 2008-205645 corrects an amplitude or a phase based on a reference transmission signal corresponding to a training signal, it is not considered that it may pursue accuracy improvement of an orientation control for a signal representing real data such as user data, etc.